The field of art to which this invention pertains is polysaccharide derivatives.
Polygalactomannans and their derivatives are well known compositions which have many uses as thickening agents in aqueous systems.
The polygalactomannans are polysaccharides composed principally of galactose and mannose units and are usually found in the endosperm of leguminous seeds, such as guar, locust bean, honey locust, flame tree and the like. Guar gum, for example, is composed mostly of a polygalactomannan which essentially is a straight chain polymannan with single membered galactose branches. The ratio of galactose to mannose units in the guar polymer is 1:2.
Locust bean gum is a polygalactomannan of similar molecular structure in which the ratio of galactose to mannose is 1:4. Guar and locust bean gums are the preferred sources of the polygalactomannans, principally because of their commercial availability.
Derivatives of polygalactomannan gums are made by reacting the gums with various derivatizing agents, which react with the hydroxyl groups of the gums to form ethers or esters. For example, hydroxyalkyl ethers of polygalactomannans are made by reacting alkylene oxides with the gums as disclosed in U.S. Pat. No. 3,483,121. The galactose and mannose sugar units of polygalactomannans each have an average of three reactive hydroxyl groups. These react with alkylene oxides to produce hydroxyalkyl ethers of the gums. Each unit of alkylene oxide added to the polygalactomannan in turn adds a new hydroxyl group which is itself reactive. Theoretically there is no limit to the amount of alkylene oxide which may be added to the polygalactomannan. As a practical matter, however, a molecular substitution (M.S.) of about 4 or 5 is a practical upper limit.
In our commonly assigned patent, U.S. Pat. No. 4,870,167, we disclose alkyl ethers of polygalactomannans wherein the alkyl groups contain 1 to 4 carbon atoms which are further modified with long chain aliphatic epoxides wherein the long chains contain 8 to about 28 carbon atoms. Such polygalactomannans are particularly useful as thickening agents for aqueous systems.
In European Patent Application No. 323,627, which was published Jul. 7, 1989, polygalactomannan derivatives containing both hydrophilic substituents and hydrophilic substituents are described.